The present invention relates to a method for detecting the molding defectiveness of a press-molded workpiece, and more particularly, to a molding defectiveness detecting method adapted for press-molding work, such as terminal press-bonding of electric wires, press-fit of heat exchanger pipes in support plates, lid grooving in the end faces of cans for beer and the like, deep press-drawing, press-marking, press-stamping, etc., and a terminal press-bonding apparatus utilizing the aforesaid method.
In attaching a press-bonded terminal to the end of a covered wire by press-molding, for example, a covering portion of a certain length is stripped from the end of a cut wire piece of a predetermined length, a wire barrel of the terminal, having a predetermined shape and dimensions, is press-bonded to a conductor portion (core portion) at the wire end, and an insulation barrel of the terminal is press-bonded to an insulating-resin-coated portion at the wire end. Some of a number of such press-bonded terminals mounted in this manner may be subject to press-bonding defectiveness at their core portion or resin-coated portion.
In these defective terminals, some of cores of the wire may be left outside the wire barrel ("split-cored"), the core portion may be wrongly seized by the insulation barrel ("sunk-cored"), or the covered portion of the wire may be seized by the wire barrel ("resin-engaged"), for example.
As a method for detecting such terminal press-bonding defectiveness, a method disclosed in Japanese Patent Disclosure No. 60-246,579 is conventionally known in which the press-bonding state is identified by detecting anything unusual during press-bonding operation, by means of a load sensor. Also proposed in Japanese Patent Disclosures Nos. 61-161,404, 61-165,645, etc. is a press-bonding defectiveness detecting method in which the press-bonding state is identified by visual recognition of processed images and the like.
In the former case, however, the unusual situation during the terminal press-bonding operation is discriminated by a load level at a certain sampling time detected by the load sensor, or the maximum load level detected. It is therefore difficult to determine the type of the abnormality, that is, whether the abnormal terminals are "split-cored" or "resin-engaged" or anything else. Practically, moreover, some abnormal terminals may be regarded as nondefective, depending on the degree of their abnormality. Thus, it is hard to accurately determine the abnormality of the products. In the latter case, on the other hand, "split-cored" terminals can be discriminated relatively easily, due to their singularity in shape. It is generally difficult, however, to identify "resin-engaged" or "sunk-cored" terminals, since they hardly manifest any differences in shape. In determining the defectiveness of terminals, moreover, it is advisable to remove defective ones after discriminating them during the press-bonding operation. Meanwhile, a press-bonding applicator and other devices are usually located above a terminal press-bonding table, so that there is no space through which the press-bonding spot can be surveyed by means of a visual recognition device, such as an ITV camera. Moreover, the press-bonding work is performed speedily and continuously. In consequence, it is difficult to obtain still images of good quality.
These circumstances are not limited to the terminal press-bonding operation for terminal-bonded electric wires, and also apply to the detection of the molding defectiveness of workpieces subjected to press-molding work, such as press-fit, press-grooving, press-stamping, deep press-drawing, etc.